End tidal sampler for an oxygen breathing mask



Aug. 6, 1968 R. G. BARTLETT, JR. ETAL 3,395,701

END TIDAL SAMPLER FOR AN OXYGEN BREATHING MASK Filed Oct. 29, 1965 5 Sheets-Sheet 1 OXYGEN IN EDWARD J. B/PUA/SMAN BYZZ a ATTORIVD AGE/1T g- 1968 R. G. BARTLETT, JR., ETAL 3,395,701

END TIDAL SAMPLER FOR AN OXYGEN BREATHING MASK Filed Oct. 29, 1965 5 Sheets-Sheet 2 SENSOR /5 Aug. 6, 1968 R. G. BARTLETT, JR. ETAL 3,395,701

END TIDAL SAMPLER FOR AN OXYGEN BREATHING MASK Filed Oct. 29, 1965 5 Sheets-Sheet 3 I INSPIRATION If V I, I y, 7b a/mosp/rere 26 T FIG. 5

SENSOR l5 A 0 SUPPLY l8 2/ 4 .J

STAGE E P #2175205 here 26 i: p

SEA/50f? /5 United States Patent 3,395,701 END TIDAL SAMPLER FOR AN OXYGEN BREATHING MASK Roscoe G. Bartlett, Jr., Lime Kiln, and Edward J. Brunsman, Silver Spring, Md., assignors to the United States of America as represented by the Secretary of the Navy Filed Oct. 29, 1965, Ser. No. 505,766 4 Claims. (Cl. 128-1465) ABSTRACT OF THE DISCLOSURE An oxygen testing apparatus comprising a multi chambered device adapted to be inserted in the lower portion of an oxygen breathing mask. A hypoxia sensor is connected to one of the chambers. A pair of flexible diaphragms form exterior walls on two of the chambers; one diaphragm being exposed to the interior of the mask and other diaphragm exposed to the ambient atmosphere. Appropriate one-way valves are provided connecting the chambers of the device whereby upon inspiration by the wearer of the mask, atmospheric pressure acting on one of the diaphragms forces the end tidal of the previous expiration into the chamber containing the hypoxia sensor, and upon expiration by the wearer the expired breath acting upon the second of the diaphragms forces the end tidal sample from the chamber containing the hypoxia sensor.

This invention relates generally to devices for sensing the amount of oxygen present in a gas and more particularlyto a device which samples the end tidal of a persons breath to indicate the amount of oxygen therein.

An important consideration for persons working in an environment where breathing oxygen must be supplied, such as aviators, divers, or firemen, is the amount of oxygen remaining in their supply. The oxygen level can, of course, be read directly from the supply tank, but in many situations a better way is to determine the amount of oxygen present in the exhaled breath of the user, for this excess is indicative of the purity and pressure of the oxygen being supplied. The prior art teaches the use of a hypoxia sensor placed loosely in the lower cavity of an oxygen mask. This loosely mounted sensor produces an unreliable output signal due to the alternating exposure to pure oxygen, as the wearer inhales, and then the exhaled carbon dioxide and low percentage of oxygen, as the wearer exhales. The instant invention teaches the use of a valve and chamber arrangement whereby the end tidal of each expiration of breath is trapped and sampled during the following inspiration. Through this arrangement pure oxygen never contacts the sensor and thus there is no fluctuating output signal produced.

It is an object of this invention to provide a means for sensing the oxygen present in the atmosphere which the inventions user is breathing.

Another object of the present invention is to provide a means for sampling the end tidal of the wearers expiration to produce a constant reliable metering signal for indicating the amount of oxygen contained in the breathing atmosphere.

It is also an object of the instant invention to provide a means for obtaining measurements of the users oxygen supply without hampering his movements.

A further object of the present invention is to provide an oxygen measuring apparatus that is compatible with other oxygen equipment now in use.

Other objects and advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when 3,395,701 Patented Aug. 6, 1968 ice considered in connection with the accompanying drawings wherein:

FIG. 1 is a view of the invention as installed in a standard type oxygen mask;

FIG. 2 is a top view of the instant invention with portions cutaway to show detail;

FIG. 3 is an elevation view of the invention taken through 33 of FIG. 2;

FIG. 4 is a diagrammatic illustration showing the flow through the invention during inspiration;

FIG. 5 is a diagrammatic illustration showing the flow through the invention during expiration; and

FIG. 6 is a diagrammatic illustration showing the flow through the invention during inspiration, and more particularly the flow of the end tidal sample of exhausted breath.

In FIG. 1 there is shown a general view of a standard oxygen mask 10, into the bottom of the internal portion of which is positioned the sampling device of the instant invention, shown generally at 11. By way of orientation are also shown oxygen inlet line 13, the top of the sampling chambers 14, and the sensor element 15. Sensor element 15 can be of any known type such as the Beckman sensor, and is of the type which can constantly sample the oxygen content of the air and signal electrically if the oxygen drops below a predetermined level. The electrical connections and actual indicating device, which can be audio or visual, are not shown and form no part of the present invention.

It is seen in FIG. 2 that the device is divided by partial wall 17 and full wall 18 into three chambers A, B, and C. Chambers A and C are further divided by means of thin flexible diaphragms, shown in more detail in FIGS. 4, 5, and 6. In the bottom section 19 of the device is a oneway exhaust valve 20 and in the top section is a one-way inlet valve 21. Upon expiration, the expelled breath passes into the device through valve 21 and exits through opening 20. In full wall 18 are one-way valves 23 and 24. It is through these valves that the end tidal sample passes to chamber C for exposure to the sensor element 15 and is then expelled. Chamber A contains an opening 25 which communicates with the atmosphere and chamber a contains an opening 26 which communicates with the upper portion of the oxygen mask and allows expiration pressure to enter chamber C.

The additional parts, the interrelationship of elements, and the operation of the device is illustrated in FIGS. 4. 5, and 6, and is hereinafter explained. The operation of this device is such that the only power needed is the power of the gas pressure in the breathing system itself. The end tidal, or last portion, of the exhaled breath of the wearer is segregated and is then forced into an area where it is in contact with the hypoxia sensor element. FIG. 4 shows a schematic diagram of the flow and valving during inspiration. As the wearer starts to inhale, valve 16, which supplies breathing oxygen to the mask, is opened and oxygen is communicated through the mask to the wearers respiratory system. The pressure of the outside atmosphere is communicated through opening 25 to chamber A to pressurize that portion of chamber A which is established by diaphragm 29. At this time valve 21 is in the closed position, as is valve 20. One of the two one-way valves in wall 18, valve 24, is opened by the pressure of gases exerted in chamber B due to the movement of diaphragm 29. This forces a portion of the gases that were in chamber B through valve 24 into chamber C and also forces diaphragm 30 to collapse. Looking now to FIG. 5, the expiration of the wearer causes oxygen supply valve 16 to be forced closed and valve 21 to open, allowing the exhausted breath to pass downward through the device. The greater portion of the exhaled breath passes immediately through valve 20 and so on out of the mask. The action of the exhaled breath in passing through chamber B also causes the inner portion of chamber A to be pressurized and diaphragm 29 collapses. At the same time, the pressure of the exhaled gases is communicated through opening 26 to the outboard portion of chamber C, behind diaphragm 30. By the action of diaphragm 30 sampling chamber C is exhausted through valve 23 and is cleared for the next sample. At the completion of the expiration by the wearer, chambers B and A are filled with exhaled gases. The end tidal of these exhaled gases stays in chamber B. Looking now to FIG. 6, it is seen that on the next inspiration by the wearer valve 16 opens, allowing breathing oxygen to enter the upper portion of the mask, while atmospheric pressure is communicated through opening 25 behind diaphragm 29 in chamber A. Since valves 21 and 20 are closed, the portion of the exhaled vapors which have been trapped in chamber B are forced by action of diaphragm 29 through valve 24 into chamber C into a position adjacent the sensing element 15, which then samples them and sends the appropriate signal.

It is thus seen that this device is entirely compatible with the standard types of oxygen masks now in use in that it does not inhibit the flow of breathing oxygen nor require any changes in the valving now present in the oxygen mask. The device is small and compact, and can be placed in a removable unit in the bottom of any standard oxygen breathing mask. It operates entirely by pressure differentials between mask and atmosphere, the only external connections being those electrical connections which would attach to the sensor element to convey the signal. This signal which the sensing element 15 would indicate is one which preferably would operate when the supply of excess oxygen exhaled has dropped beneath a tolerable level, this being indicative of oxygen purity and pressure being supplied for inhalation.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is: 1. An end tidal oxygen sampler for use in an oxygen breathing mask comprising:

a sampling chamber, valve means connecting said sampling chamber with the interior of said mask and the ambient atmosphere,

an oxygen sensor element in communication with said sampling chamber and operable to indicate when the level of oxygen in the sampled atmosphere is below a predetermined level,

means operable by atmospheric pressure for forcing the end tidal into said sampling chamber, and means operable by the pressure of the users expiration to force the end tidal from said sampling chamber after exposure to said oxygen sensor element. 5 2. The structure set forth in claim 1 and wherein said means for forcing the end tidal into said sampling chamber comprises:

a first chamber a first diaphragm dividing said first chamber into an inner section in communication with said sampling chamber and an outer section in communication with the atmosphere, whereby the pressure differential between the mask pressure and atmospheric pressure causes said diaphragm to inflate and force the end 15 tidal into said sampling chamber.

3. The structure set forth in claim 2 and wherein said valve means comprises:

a second chamber interposed between said first chamber and said sampling chamber, said second chamber being in open communication with said first chamber and communicating with said sampling chamber by means of a pair of oppositely acting one-way valves,

a one-way inlet valve in said second chamber for allowing the expiration of the wearer to pass thereto, and

an exhaust opening in said second chamber for allowing the expiration to exit,

whereby the end tidal in said second chamber is forced into said sampling chamber by the action of said first diaphragm.

4. The structure of claim 3 wherein said means for forcing the end tidal from the sampling chamber comprises:

a second diaphragm dividing said sampling chamber into an inner section in communication with said second chamber by means of said pair of oppositely acting one-way valves, and an outer chamber in communication with the pressure of the wearers expiration, whereby the pressure of the wearers expiration inflates said second diaphragm to force the sampled end tidal out of said inner section of said sampling chamber.

References Cited UNITED STATES PATENTS 4/1958 Finney 128-142 8/1961 Holm et a1 128140 

